This relates generally to test systems, and, more particularly, to optimizing test setups for over-the-air test systems with channel model emulation capabilities.
Electronic devices often incorporate wireless communications circuitry. For example, devices may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz. Communications are also possible in cellular telephone telecommunications bands and other wireless bands. In schemes such as multiple-input-multiple-output (MIMO) schemes, an electronic device may use an array of multiple antennas to handle wireless communications.
The wireless communications circuitry of an electronic device typically undergoes evaluation during development. For example, an antenna design may be evaluated to determine whether changes are needed before a device is released for large-volume manufacturing. If it is determined that an antenna design is not performing as well as desired, design changes can be made. For example, in a MIMO arrangement, additional antennas could be added. Changes could also be made to the placement of the antennas in a device and the types of antennas being used.
One way to evaluate wireless communications circuitry is to use conducted tests. In conducted tests, test equipment is connected to the radio-frequency circuitry of a device under test (DUT) directly using cables. Standards organizations have developed standardized channel models that can be used to represent a real-world communications path in a MIMO system. A channel model may, for example, be used to represent a communications path that includes reflections and other signal impairments, motion of the mobile station (DUT), etc. During conducted tests, a channel emulator may be used to emulate the signals associated with a given channel model.
In some situations it may be desirable to evaluate the performance of a DUT using over-the-air (OTA) radio-frequency signals. In a typical OTA test system, radio-frequency signals are transmitted from an OTA test system antenna to an antenna in a DUT. OTA tests may provide information on the performance of a particular design that might not otherwise be obtained using conducted tests with a channel emulator. For example, OTA tests may reveal information on how the shapes and placements of antennas in a MIMO array affect performance. OTA tests may also provide insight into the interplay between the housing and other portions of a DUT and the antennas in the MIMO array.
When performing OTA tests, it would be desirable to be able to use the same types of channel models that are available when performing conducted tests using channel emulators. This would allow a comparison of conducted test results and OTA test results and would help ensure that OTA test results accurately reflect the real world conditions that are modeled using the channel model.
It would therefore be desirable to be able to provide design and analysis tools that assist test personnel in optimizing an OTA test system so that OTA test results closely match the theoretical results expected from a channel model and that assist test personnel in performing other test functions.